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Implication and equivalence constraints

Description
Defining logical constraints (implication, equivalence).

Further explanation of this example: 'Xpress Kalis Reference Manual'


Source Files





impequiv.mos

(!****************************************************************
   CP example problems
   ===================
   
   file impequiv.mos
   `````````````````
   Logical constraints (implication, equivalence).

   (c) 2008 Artelys S.A. and Fair Isaac Corporation
       Creation: 2005, rev. Mar. 2013
*****************************************************************!)
model "Logical constraints"
 uses "kalis"

! Default bounds for all variables
 setparam("KALIS_DEFAULT_LB", 0); setparam("KALIS_DEFAULT_UB", 5)
  
 declarations
  A, B, C, D, E: cpctr
  x,y,z,b: cpvar
 end-declarations

 setname(b, "b"); setname(x, "x")
 setname(y, "y"); setname(z, "z")
 b <= 1

! Definition of constraints (without posting)
 A:= x >= y + 5 + z + b
 B:= b = 1
 C:= all_different({x, y, z})    ! Cannot be used with 'equiv'
 D:= y <= z
 E:= distance(y,z) <= 2

 writeln("Original domains: ", b, " ", x, " ", y, " ", z) 
 
! If x, y and z are all different then b equals 1 (C=>B),
! if b equals 1 then x, y and z are all different (B=>C).
 implies(C, B)
 implies(B, C)

! E<=>B: b equals 1 if and only if |y-z| <= 2
 equiv(E, B) 

! A<=>D: x >= y + 5 + z + b if and only if y <= z
 equiv(A, D)
 
 writeln("With constraints: ", b, " ", x, " ", y, " ", z)

 while (cp_find_next_sol)  
  writeln("Solution: ", b, " ", x, " ", y, " ", z)

end-model

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